This should be included in all themes by default. In fact, I wouldn't mind a nice bottom icon saying "Printable CSS page" or something, alongside the "powered by tikiwiki", because most users will be pleasantly surprised by this function.
(same login on en.wikipedia, use my talk page there to get in touch with me)
I agree for the css print. Right now, many features do not offer a print option. It would especially nice for trackers.
Can you do it?